This invention relates to a magnetic display panel mainly applied to picture drawing b y infants and a method for manufacturing the same, and more particularly to a magnetic display panel improved in structure by integrally combining a core block and a member for sealing both sides of the core block with each other and a method for manufacturing the same.
As a drawing board for infants, a magnetic drawing panel has been conventionally known in the art, which includes a transparent or semi-transparent drawing plate or a base plate, a plate-like face member arranged opposite to the base plate, and a honeycomb core including a number of hexagonal cells and sealedly arranged between the base plate and the plate-like face member wherein the cells each are sealedly charged therein with a plastic dispersion liquid containing magnetic particles.
In the conventional magnetic drawing panel thus constructed, a magnetic pen is contacted at a tip thereof with a drawing faceplate of the plate-like face member to act a magnetic field on the dispersion liquid, to thereby permit the magnetic particles kept sinking on a bottom of the cells to rise to the drawing faceplate of the plate-like face member, resulting in displaying a picture or a character on the drawing faceplate due to a difference in contrast between the dispersion medium and the magnetic particles. Also, movement of an erasing bar provided thereon with a magnet or the like under the base plate permits the rising magnetic particles to sink on the bottom of the cells, leading to erasure of the picture or character drawn.
Infants often take an unpredictable action. For example, they often strongly knock or hit the tip of the magnetic pen against the base plate of the magnetic drawing panel. This possibly causes the drawing faceplate to be broken or a wall of the honeycomb core to be deformed due to impact of the magnetic pen, resulting in joining between the drawing faceplate and the honeycomb core being broken.
Breakage of the drawing faceplate causes the plastic dispersion liquid encapsulated in the cells to leak out, so that infants possibly stain their clothing, drink the liquid by mistake or get it into their eyes. The plastic dispersion liquid adhering to clothing is hard to come off, to thereby render washing of the clothing highly troublesome or substantially impossible. More fearfully or troublesomely, drinking of the liquid by infants by mistake possibly causes the infants to damage their stomach and intestines, because the dispersion liquid contains magnetic particles made of metal. Likewise, getting of the liquid into infants"" eyes possibly leads to damages to a surface of the eyes due to infants"" unintentional rubbing of the eyes. Further, breakage of the drawing faceplate tends to cause a broken portion thereof to be acute, so that the broken portion of the drawing faceplate may possibly damage parts of the body such as the hands, arms or the like. In addition, the magnetic display panel is substantially applied to infants. Thus, the magnetic display panel is required to exhibit satisfactory safety to the internal organs and body of the infants.
Also, deformation of a part of the drawing faceplate due to the above-described impact of the magnetic pen often leads to breakage of a joint between the drawing faceplate made of a relatively rigid vinyl chloride material and the honeycomb core, resulting in the adjacent cells communicating with each other through the broken joint. This will be more detailedly described with reference to FIGS. 12A and 12B. When a drawing faceplate 22 is deformed, to thereby be formed with a deformation, cells 20 adjacent to each other are caused to communicate with each other through a joint therebetween positioned at the deformation, so that a plastic dispersion liquid 21 in the cells 20 flows between the cells through the joint. Meanwhile, charging of the plastic dispersion liquid 21 into a honeycomb core causes air to be introduced into the liquid 21, resulting in the air forming bubbles in the liquid. Stirring of the plastic dispersion liquid 21 permits bubbles of a large size to burst, to thereby be discharged to an ambient atmosphere. However, microsized bubbles 25 are taken in the plastic dispersion liquid 21 in spite of the stirring, resulting in remaining in the liquid, because the plastic dispersion liquid 21 exhibits properties like an emulsion. When the magnetic display panel thus constructed is operated to slide a magnetic pen on the adjacent cells 20 while a partition 23 between both cells 20 is kept broken, a pressure in the cells 20 is varied when a pressure of the magnetic pen is applied to the cells. Also, forced movement of the magnetic drawing panel causes the plastic dispersion liquid in each of both cells 20 to flow therebetween. Thus, the micro-sized bubbles 25 present in the plastic dispersion liquid 21 of both cells 20 are caused to collide with each other during flowing of the liquid, to thereby be gradually increased in size. Such growth or increase in size of the bubbles causes the bubbles to rise in the plastic dispersion liquid 21, resulting in the bubbles being adhered to a rear side of the drawing faceplate 22. Such situation fails to permits the magnetic particles 23 to rise to the rear surface of the drawing faceplate 22 even when it is attempted to rub the drawing faceplate 23 with the magnetic pen to carry out rising of the magnetic particles, because the thus-growing bubbles 25 interfere with rising of the magnetic particles in the plastic dispersion liquid 21. This renders external observation of the magnetic particles through the drawing face plate 22 impossible or highly difficult, resulting in lines drawn on the drawing faceplate 22 being highly indistinct.
Further, in the conventional magnetic drawing panel, the base plate, drawing faceplate and honeycomb core each are made of vinyl chloride. This causes the magnetic drawing panel to readily generate static electricity. In particular, in the winter in which air is dried, static electricity is readily charged on the magnetic drawing panel. Charging of static electricity on the magnetic drawing panel causes the magnetic particles to be attracted onto the base plate and drawing faceplate to a degree sufficient to interfere with smooth flowing of the magnetic particles by magnetic force of the magnetic pen, leading to a variation in brightness or contrast of a line drawn on the drawing faceplate or a failure in drawing of a line thereon. Thus, in the conventional magnetic drawing panel, it is required to move an erasing bar throughout the magnetic drawing panel to facilitate flowing of the magnetic particles prior to operation of the magnetic drawing panel. Unfortunately, this renders handling of the magnetic drawing panel troublesome.
In addition, formation of vinyl chloride into the honeycomb core causes an end surface of each of the cells to be relatively thick. Thus, when any external light is reflected by the end surfaces of the cells, a configuration of the honeycomb is caused to be projected on the drawing faceplate. This reduces an effective area of the drawing faceplate and often deteriorates free drawing.
Furthermore, the magnetic display panel made of vinyl chloride generates toxic dioxin when it is incinerated at a low temperature for disposal. Dioxin is considered to have any relationship to a so-called environmental hormone although it is not sure because of being under investigation. In particular, the magnetic display panel is applied to infants, therefore, it is required not only to be fully safe by itself but not to damage to the human body when it is subject to disposal. Thus, it is highly demanded to develop a means of safely disposing of the magnetic drawing panel.
In the conventional magnetic display panel, encapsulation of the plastic dispersion liquid containing the magnetic particles in the cells of the honeycomb core is carried out by adhering open end surfaces of the honeycomb core formed on both sides thereof to the base plate and plate-like face member, respectively. More particularly, the base plate, plate-like face member and honeycomb core each are made of vinyl chloride. Subsequently, the honeycomb core is heated to a softening point thereof utilizing thermoplasticity of vinyl chloride and then the open end surfaces of the cells of the honeycomb core is collapsed while being melted, to thereby be joined to the base plate and plate-like face member. Alternatively, an adhesive is coated on a rear surface of the plate-like face member and then the face member is heated while being forced against the open end surface is of the honeycomb core after the adhesive is dried, resulting in melting the adhesive, so that the face member may be adhered to the honeycomb core by means of the thus-melted adhesive.
Unfortunately, both techniques described above have a disadvantage that the heating temperature is excessively high, to thereby cause the honeycomb core to be softened, resulting in rigidity of the honeycomb core being deteriorated, leading to deformation of the drawing faceplate. Whereas, a reduction in heating temperature tends to lead to a failure in adhesion between the honeycomb core and the plate-like face member and/or base plate.
Rugged deformation of the base plate and/or plate-like face member not only deteriorates a commercial value of the magnetic display panel but fails to ensure smooth movement of the magnetic pen, to thereby deteriorate operability of the pen. Also, any possible failure in joint between the base plate and the honeycomb core causes the cells adjacent to each other at the failed joint to communicate with each other.
Thus, the prior art requires to control a heating temperature during manufacturing of the magnetic display panel, so that the manufacturing may be highly troublesome.
The present invention has been made in view of the foregoing disadvantages of the prior art.
Accordingly, it is a primary object of the present invention to provide a magnetic display panel which is capable of ensuring safety to infants to minimize damage to the bodies of the infants in view of the fact that such a magnetic display is applied to substantially only infants. It is another object of the present invention to provide a magnetic display panel which is capable of substantially preventing damage to a drawing faceplate and breakage of a joint between the drawing faceplate and a honeycomb core when the drawing faceplate is strongly pushed with a tip of a magnetic pen, to thereby ensure safety to the body of infants. It is a further object of the present invention to provide a magnetic display panel which is capable of permitting a distinct line to be drawn thereon. It is still another object of the present invention to provide a magnetic display panel which is capable of ensuring safe disposal of the magnetic display panel without causing any environmental pollution when it is waste.
It is yet another object of the present invention to provide a method for manufacturing a magnetic display panel which is capable of facilitating temperature controlling to increase manufacturing efficiency and ensuring safe disposal thereof without causing environmental pollution and harming health.
In accordance with one aspect of the present invention, there is provided a magnetic display panel which is capable of solving the above-described problems of the prior art. The magnetic display panel includes a core housing which has a peripheral edge formed to have an increased height and is formed therein with a recess, a plate-like face member arranged so as to cover the recess of the core housing, and a core block provided with a number of cells in which a plastic dispersion liquid containing magnetic particles is encapsulated and sealedly joined between the core housing and the plate-like face member by means of an adhesive. The core housing and plate-like face member are each made of olefin synthetic resin. One of the core housing and plate-like face member constitutes a drawing faceplate, which is formed to be transparent or semi-transparent. The core block is formed of pulp made paper.
The core block may be formed of glassine paper. Alternatively, it may be formed of parchment paper.
The core housing may be formed of a material selected from the groups consisting of polyethylene terephthalate, polyethylene and polypropylene.
The adhesive may be formed of a material selected from the group consisting of an vinyl acetate resin adhesive, an acrylic resin adhesive and an ultraviolet-curing adhesive.
The recess of the core housing preferably has an upper end formed to be higher than an upper end of the honeycomb core.
A difference in height between the upper end of the recess of the core housing and that of the honeycomb core is preferably set to be larger than 0 and 0.1 mm or less.
The plastic dispersion liquid preferably contains a coloring agent which has a color similar to that of the core block.
In accordance with another aspect of the present invention, a method for manufacturing a magnetic display panel is provided. The method includes the steps of forming olefin synthetic resin into a core housing which has a peripheral edge formed to have an increased height and is formed therein with a recess and arranging a core block in the recess of the core housing. The core block is made of paper and provided with a number of cells. The method also includes the steps of bonding the core block and the recess of the housing to each other by means of an adhesive, charging a plastic dispersion liquid containing magnetic particles in the core block and arranging a plate-like face member in a manner to be opposite to the core housing with the core block being interposed between the plate-like face member and the core housing. The plate-like face member is made of olefin synthetic resin. The method further includes the steps of applying an adhesive to a rear surface of the plate-like face member and bonding the rear surface of the plate-like face member to an open surface of the core block to encapsulate the plastic dispersion liquid in the cells.
The adhesive is preferably a room temperature curing adhesive or an ultraviolet-curing adhesive.
The core block is preferably a honey comb.
The step of bonding the plate-like face member to the open surface of the core block may be carried out by moving the plate-like face member along the open surface of the core block while forcing the plate-like face member against the open surface of the core block using any suitable means. Alternatively, it may be carried out by forcing the plate-like face member against the open surface of the core block using any suitable press means.